Phonatory modifications of auditory origin (Académie de Médecine 1957)
Communication presented to the Académie nationale de médecine on 4 June 1957 by Raoul Husson, Docteur ès-Sciences, Maître de Recherches at the C.N.R.S., and published in the Bulletin de l’Académie Nationale de Médecine (vol. 141, nos. 19 and 20). Presentation made by M. Moulonguet. A founding document: it is in these seven pages that Husson, taking up and confirming experimentally at the Sorbonne the observations published by Alfred Tomatis in 1954, for the first time designates under the name “Tomatis Effect” the set of audio-phonatory feedback responses that make the voice the acoustic mirror of the ear. Husson sets out the experimental apparatus, the correspondence between auditory frequency bands and the laryngo-pharyngo-buccal muscle groups, and the therapeutic applications (alterations of laryngeal tone, velar pareses).
Phonatory modifications of auditory origin and physiological and clinical applications
by M. Raoul HUSSON
Docteur ès-Sciences — Maître de Recherches at the C.N.R.S.
(Presentation made by M. Moulonguet)
Extract from the Bulletin de l’Académie Nationale de Médecine — Vol. 141, nos. 19 and 20 — Session of 4 June 1957.
I. — Introduction
1° Tomatis reported, in 1954 [1], a fact of the greatest interest: if a subject utters a vowel into a microphone whose voltage is passed through a filter that suppresses a certain band of frequencies before being returned to earphones placed on the subject’s ears, the band in question is likewise suppressed from the subject’s voice. By the same process, and still according to the same author, the voice of a subject afflicted with an auditory scotoma is amputated of the harmonics that would be contained in the entire suppressed island. Tomatis crystallised these facts in the formula: “The voice contains only the harmonics that the ear is capable of hearing.”
The present work was undertaken with a view to studying in their detail the singular phenomena synthesised above and to elucidating their neurological mechanism of realisation. To this end we used differential frequency amplifiers built by the engineer L. Pimonow, devices which allow, within a complex supply (periodic or otherwise), the intensities of given frequency bands to be selectively increased or decreased. A first device was loaned to us by Mr L. Pimonow himself and used in the Laboratoire de Physiologie at the Sorbonne. The second was used at the Hôpital Laënnec with the kind permission of Dr R. Maspetiol and the obliging assistance of Dr D. Semette. We operated on subjects of both sexes (1), with uncultivated or cultivated voices, and notably on numerous powerful-voiced artists of the Réunion des Théâtres Lyriques nationaux, in every register and across the full extent of each tessitura.
II. — Results of experiments carried out by imposing on the subject homorhythmic supplies, but different from those that they emit
2° Experimental set-up. — The subject emits a held vowel (supply F) into the microphone, whose voltage is directed to the differential frequency amplifier, which transforms it into a supply F’ modified at the operator’s will. Supply F’ is sent into the subject’s ears by means of double earphones on a headset. One observes how the emitted supply F is modified under the effect of the auditory stimulation. Monitoring at the frequency analyser and the laryngostroboscope where appropriate.
3° Case of auditory stimulating supplies F’ very close to the emitted supply F. — If the supply F’ imposed on the ear represents a real vowel acoustically close to the one F that is emitted, the laryngeal or pharyngo-buccal modifications enabling the passage from F to F’ are achieved at once, completely and without difficulty (without the subject emitting F being aware of it). This is notably the case:
a) If the intensities in the 2,500-3,500 band of F’ are slightly increased, the same increase appears in F through an increase in the tone of the glottic sphincter (verifiable at the laryngo-stroboscope);
b) If the intensities in the buccal (or pharyngeal) formant band of F’ are slightly increased, the same increase appears in the buccal (or pharyngeal) formant band of F through a slight postural adaptation of the buccal (or pharyngeal) cavity which amplifies the corresponding resonance state.
4° Case of auditory stimulating supplies F’ further from F, but still physiologically achievable. — If the supply F’ presents to the ear a vowel as far removed from the F that is emitted as may be, the emission spontaneously shifts towards F’ (with a certain evolution) only to a certain extent, which follows along with the subject. This is notably the case: a) If one increases (or decreases) the intensities in the 1,200-1,800 cycle band of F’, one decreases (or increases) the nasality of the emitted F by inducing a slight raising (or lowering) of the velum. That is, the intensities of all the constituents above 500 cycles (for example) of F’ undergo an equivalent drop in F, bearing chiefly on the 2,500-3,500 band, through induced hypotonisation of the larynx (verifiable at the laryngo-stroboscope).
5° Case of auditory stimulating supplies F’ not physiologically achievable, or too distant from F. — If the supply F’ imposed on the ear is too different from the F that is emitted, or else if it does not represent a physiologically achievable supply, nothing further occurs: the subject returns to the emission of F alone, perceiving only a slight diffuse organic discomfort. This is notably the case: a) If F is suppressed simultaneously in spoken voice in such a way as to deprive F’ of its vocalic character. b) If both formants F and F’ are written in such a way as to confer on F’ a very different vocality from that of F (open O changes to U, or open A/E changes to E, for example).
6° General interpretation of these phenomena. — The body of results above may be interpreted as follows: when the subject emits a supply F, transformed by filtering into a supply F’, it can be that one passes from the supply F’ to F. The latter, perceived by the auditory cortex in the form of an integration image where the necessary order is realised to provoke (in the subject), awakens the vocal body schema of F. The latter, in principle different from the vocal body schema of F, provokes adjustment reactions adequate for F and not for F. By way of feedback, the subject very quickly achieves regulations of pharyngo-buccal posture and adjustments of laryngeal tone that allow the realisation of the supply F’ and no longer that of F.
The auditory sensory contribution, corrected by the “gamma” fibres which ensure intra-fusal stimulations, governs the proprioceptive regulation of muscular origin, as is observed in the visual corrections of the phenomena of equilibration (2).
It is fitting to give to these phenomena of feedback of auditory origin which, when they occur, modify the supply (or model) emitted F, the name “Tomatis Effect”, after the author who first observed and described them.
7° Subsidiary experimental observations.
a) The highly differentiated phenomena described above (§§ 3, 4 and 5) are all the more distinct as the supply (or model) F’ imposed auditorily is more intense and the better it effaces the F that is present; and if F’ is too weak, all feedback disappears.
b) In professional singers, the feedback responses are remarkably distinct, and manifest themselves all the better as the subject is accustomed to appreciating their vocal body schema with a view to directing their emission in timbre and quality.
c) In wholly uncultivated voices, the feedback responses of the transformation of F into F’ occur practically with the same ease as in the schemas (case of § 3).
d) The feedback responses also occur in spoken voice, and sometimes more readily, which is explained by the fact that the subjects already have the formation of passive vocal body schemas (linked to the functional stereotypies of habitual speech) whose conscious deployment is practically immediate.
e) The feedback responses bearing on the adjustment of laryngeal tone occur far more readily (they take place almost invariably) than those involving the re-establishment of the postural configuration of the pharyngo-buccal trumpet (which often merely get under way).
III. — Correspondence between the altered frequency bands and the muscle groups activated by feedback
8° The analysis of these phenomena makes it possible to assign a rough but clear correspondence between the modified frequency bands and the muscle groups upon which the feedback acts. It is very striking that, in this correspondence, the cut-off frequency [3, 4] of the pharyngo-buccal trumpet plays the essential role (3).
a) By increasing the intensity of harmonics above the cut-off frequency, the larynx responds by an increase of the tone of vocal-fold closure (which sharpens the voice’s edge, the intensity of the high harmonics previously being above this frequency). Inverse phenomena when acting by decrease.
b) By acting on harmonics below the cut-off frequency, one no longer modifies the tone of the laryngeal sphincter, but instead determines exclusively postural adaptations of the pharyngo-buccal trumpet. In particular, if one acts upon the 1,200-1,800 cycle frequency band, one effectively induces a decrease or an increase of nasalisation [4]: that is, it provokes a marked lowering or raising of the velum. By acting selectively on the formantic tonal zones themselves, one provokes pharyngeal or buccal adaptations (which, most often, merely get under way).
IV. — Various consequences for phonatory physiology and physiopathology
9° The phenomena of feedback of auditory origin, operating through the vocal body schemas upon the laryngo-pharyngo-buccal muscle groups involved in phonatory realisations, presumably intervene (though not exclusively) in the explanation of the well-known phenomena of educational vocal mimicry, whether the familial vocal mimicry of children or the recognised facilitating effects of example in the teaching of singing.
b) They presumably likewise intervene in the realisation of the curious phenomena reported long ago by A. Labriet (1925) and termed by him “vocal accord” [5]: in trained singers, the accord of a cavity (pharyngeal or buccal) is sometimes completed on a constituent of the laryngeal supply by spontaneous accommodation when the resonance state achieved is sufficiently close to a resonance maximum.
c) These phenomena have a direct application, already in use [1], in the therapy of functional alterations of the tone of the laryngeal sphincter. In cases of tonal drops occasioned in particular by inhibitory afferences (issuing from the digestive tract or of hypothalamic origin), the excito-tonic contribution resulting from auditory stimulations of the 2,500-3,500 band suffices invariably to restore a firm closure of the vocal folds, and allows the subject to recover their habitual vocal body schema. After a stimulation of a few minutes, the recovery lasts several hours and, by iteration, eventually becomes permanent.
d) These phenomena may also be used in the therapy of functional decreases of the motility of the velum, and notably in velar pareses (slight permanent nasalisations): it suffices to subject the patient to an auditory stimulation localised to the 1,200-1,800 cycle band. In cases of both velar and laryngeal paresis (often observed), it will suffice to stimulate both the 1,200-1,800 and the 2,500-3,500 bands, or simply all frequencies above 1,200 cycles.
Notes
(1) Our thanks go most especially to MM. Georges Vaillant and Ernest Blanc, of the Opéra, and Roger Gallia, of the Opéra-Comique; to Mlle Irène Bonneau; to Dr Hénin and to Drs Garde, Labarraque, Hénin, Horowitz (of London) and de Leval (of Liège).
(2) This important remark is due to Professor André Soulairac, whom I warmly thank moreover for the precious help he kindly afforded me in the elaboration of this delicate interpretation.
(3) When a trumpet serves to externalise sound waves issuing from a source (the case of the human vocal organ), waves whose frequency is below a certain limit retain the air of the trumpet en bloc, without appreciable propagation: above this limiting frequency (called the “cut-off frequency”), the waves do propagate effectively within the trumpet, with maximum externalisation [4]: the conditions of propagation of the waves are markedly different for frequencies below and above this cut-off frequency of the pharyngo-buccal trumpet. For the voice, the cut-off frequency depends on the dimensions of the buccal cavity, but on average lies between 1,200 and 2,200-2,500 cycles.
Bibliography
[1] A. TOMATIS, Rôle directeur de l’oreille dans le déterminisme des qualités de la voix normale (parlée et chantée) et dans la genèse de ses troubles. Actualités Oto-Rhino-Laryngologiques, Masson, Paris, 1954, 264.
[2] A. SOULAIRAC, Sensibilités internes et phonation. Revue de Laryngol. Portmann, Suppl. de novembre 1955, 666-674. — Rôle des sensibilités internes en psychophysiologie. Course given at the Sorbonne, 2nd semester 1954 (unpublished).
[3] R. HUSSON and L. PIMONOW, Facteurs acoustiques des voyelles (non nasalisées) et fréquence de coupure du pavillon pharyngo-buccal. C.R. Acad. Sc. Paris, 1957, 244, 1261.
[4] Y. ROCARD, Propagation et absorption du son. Actual. Scient. et Industrielles, Hermann, Paris, 1935, no. 222, 13-39. — Dynamique Générale des Vibrations, Masson, Paris, 2nd ed., 1953, 374 et seq.
[5] A. LABRIET and R. HUSSON, Principe de l’accord vocal, ou contribution à l’élaboration d’une théorie de l’émission normale de la voix chantée. C.R. Acad. Sc. Paris, 1925, 180, 1680. — Principes d’éducation vocale par la réalisation de l’accord vocal. C.R. Acad. Sc. Paris 1925, 181, 358.
Editor’s note
This communication by Raoul Husson is not signed by Alfred Tomatis, but it constitutes the founding document in which the phrase “Tomatis Effect” appears for the first time, under the pen of a Sorbonne physiologist. Husson, having reproduced experimentally with his differential amplifiers the observations published by Tomatis in 1954 (“the voice contains only the harmonics that the ear is capable of hearing”), concludes his interpretative section with this decisive sentence: “It is fitting to give to these phenomena of feedback of auditory origin (…) the name ‘Tomatis Effect’, after the author who first observed and described them.” We therefore reproduce this historic text in full, as the necessary counterpart to the publications by Tomatis himself gathered on this site.
Source: Husson R., “Modifications phonatoires d’origine auditive et applications physiologiques et cliniques” (presentation made by M. Moulonguet), Bulletin de l’Académie Nationale de Médecine, vol. 141, nos. 19 and 20, session of 4 June 1957, pp. 9-15 of the offprint. Digitised document from the personal archives of Alfred Tomatis.